<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        html,body {
            height: 100vh;
        }
        .content {
            height: 100vh;
            border-color: red;
        }
        .box1 {
            height: 100px;border-color: green;
        }
        .box2{
            position: absolute;
            top: 100px;
        }
    </style>
</head>
<body>
    
</body>
</html>